You can do it from any web page as well. Here is an example.
If you are on a web page and there is a pic you want to put on here just right click on the image and you will get several options. The exact wording of the option you want depends on the browser you are using.
On Firefox the option is "copy image location" on safari it is "copy image address".
Then at the top of the text box that we type in to post, there is an icon of mountains and a sun, hover over that and it says insert image.
Click that icon, a box will pop up that says insert the url of your image
just paste what you copied from the web page you were visiting.
and you get something like
the code looks like this: